Harvestmen (or Daddy-longlegs) are eight-legged invertebrate animals belonging to the order Opiliones. If you look at the body of a Daddy-longlegs with your magnifying glass, you'll see why it's not a spider. First of all, instead of its body consisting of two parts, the cephalothorax and the abdomen, as with spiders, there's just one thing. A Daddy Longlegs has its head, thorax, and abdomen all fused together. Second, instead of the spider's usual eight eyes, a Daddy Longlegs just possesses two.